Difficulty setting up SchoolTool on port 80 externally

Hello,

I'm attempting to setup a test SchoolTool instance on http://lcchs.ddns.net - and it is working, but only on my local network.

What I've done is left paste.ini on host 127.0.0.1 and followed the Apache configuration instructions to proxy from port 80 external to local port 7080:

<VirtualHost *:80>
  ServerName lcchs.ddns.net

  <Proxy *>
      order allow,deny
      allow from all
      deny from none
  </Proxy>

  ProxyPreserveHost on
  RewriteEngine On

  RewriteRule ^/schooltool.task_results(/?.*) http://127.0.0.1:7080/schooltool.task_results/$1 [P,L]
  RewriteRule ^(/?.*) http://127.0.0.1:7080/++vh++http:lcchs.ddns.net:80/++$1 [P,L]

</VirtualHost>

Wht happens now is that on my local area network, http://lcchs.ddns.net loads up fine (good), http://10.1.1.9/ gives me the Apache welcome page (seems dodgy) and http://10.1.1.9:7080 does not work (good).

Connecting to http://lcchs.ddns.net from an external network gives this message: http://i.imgur.com/QxHFCmf.png, and diagnostics for it say:

CacheHost: tx22rrpep32a
ErrPage: ERR_READ_ERROR
Err: (104) Connection reset by peer
TimeStamp: Tue, 16 Jun 2015 22:52:24 GMT

ClientIP: 10.67.10.248
ServerIP: 124.170.74.158

HTTP Request:
GET / HTTP/1.1
Host: lcchs.ddns.net
Connection: keep-alive
Cache-Control: max-age

ERR_READ_ERROR seems to be a Squid cache error - I've got no idea where that is coming from, maybe the ISP.